Catalytic carbonylation of olefinic and acetylenic compounds to form oxygenated derivatives with an increased content of carbon atoms is a well-established technology. Various developments and improvements are described in U.S. patents such as U.S. Pat. Nos. 2,768,968; 2,863,911; 2,876,254; 3,040,090; 3,455,989; 3,501,518; 3,507,891; 3,652,655; 3,660,439; 3,700,706; 3,723,486; 3,746,747; 3,755,419; 3,755,421; 3,793,369; 3,856,832; 3,859,319; 3,887,595; 3,906,015; 3,917,677; 3,952,034; 3,992,423; 4,102,920; 4,245,115; 4,246,183; and references cited therein.
Of interest with respect to the present invention is the chemical literature relating to dimeric carbonylation of aliphatic conjugated dienes in the presence of a hydroxylated coreactant and a catalyst complex of a Group VIII noble metal and a Group VA tertiary donor ligand. The dimeric carbonylation reaction is illustrated by the following chemical equation with respect to the interaction of 1,3-butadiene with alkanol: ##STR1##
In a report published in Tetrahedron, 28, 3721 (1972), there is described a dimeric carbonylation of 1,3-butadiene in the presence of alkanol and a palladiumphosphine complex catalyst to yield alkyl 3,8-nonadienoate. The publication discloses that the absence of halide coordinated to the palladium metal is essential for the formation of alkyl nonadienoate product. In the presence of halide, one mole of 1,3-butadiene reacts with one mole of carbon monoxide and one mole of alkanol to yield alkyl 3-pentenoate.
U.S. Pat. No. 4,124,617 describes a process for the selective production of fatty acid derivatives from aliphatic diene substrates, in the presence of dual-function homogeneous palladium complexes and certain classes of organic tertiary nitrogen bases. One aspect of this type of process is that the use of tertiary nitrogen bases promotes the production of various byproducts such as C.sub.5 --esters. Another aspect is that the catalyst tends to exhibit a reaction rate decrease during the course of the carbonylation reaction due to instability of the catalyst system.
Also of interest with respect to the present invention is the chemical literature relating to hydroesterification of alpha-olefins to yield alkanoate esters.
In J. Org. Chem., 41, 793(1976) and J. Org., Chem., 41, 2885(1976) there is reported the synthesis of linear carboxylate esters from alpha-olefins in the presence of a homogeneous platinum complex catalyst: ##STR2##
U.S. Pat. No. 3,933,884 describes a process for preparing thioloesters by the interaction of an alpha-olefin with carbon monoxide and a thiol compound in the presence of a catalyst composed of a noble metal halide and a Group IVB metal halide and a Group VB donor ligand.
There is continuing development effort directed to improvement of processes and catalysts for carbonylation and hydroesterification of olefinic substrates to yield oxygenated or sulfurated derivatives of increased carbon content via monomeric and dimeric reaction mechanisms. There has not been any prior art directed specifically to monomeric thioloesterification of 1,3-alkadiene compounds.
Accordingly, it is a main object of this invention to provide an improved process for conversion of aliphatic conjugated dienes into fatty acid derivatives.
It is another object of this invention to provide a process for producing alkyl thioloalkenoate by monomeric thioloesterification of 1,3-alkadiene with high conversion and selectivity to linear product.
It is a further object of this invention to provide a stabilized palladium catalyst system adapted for thioloesterification of olefinic hydrocarbons.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.